as others pointed out, it is a lot more productive if you plot all the data on the map, as you put down the various data points, you can easily determine target course, speed, range and AOB using the in game tools,
for example, here, by plotting two data points, measuring the time in between, we have target course 68 degrees east, speed 5 knots.
Here by measuring where I want to shoot, i.e. on a bearing of 350, I get a range of 950 meters and AOB of 76 degrees.
obviously the closer you are, the less precise you have to be, in part because the target will cover several degrees.